Over several decades, research in communication, social psychology, and marketing has examined how characteristics of a message source influence persuasion. One of the most influential frameworks in this domain is Source Credibility Theory, originally developed within the Yale tradition of persuasion research. This theory posits that the effectiveness of a persuasive message depends largely on the perceived credibility of its source, a concept primarily defined by expertise and trustworthiness (Hovland et al., 1953).

Expertise refers to the extent to which a communicator is perceived as knowledgeable, skilled, and competent in a given domain, whereas trustworthiness reflects perceptions of honesty, sincerity, and objectivity. According to Source Credibility Theory, messages delivered by highly credible sources are more likely to be accepted, internalized, and retained over time than those conveyed by low-credibility sources. The underlying mechanism is internalization, whereby individuals adopt beliefs or attitudes because they perceive the information as valid and accurate, independent of the source’s presence (Hovland et al., 1953; Sternthal & Craig, 1973).

Parallel to this line of research, the source attractiveness model emphasizes a different route to persuasion based on identification rather than internalization. Attractiveness is conceptualized broadly and includes physical attractiveness, familiarity, likability, and perceived similarity between the source and the receiver (McGuire, 1985). Persuasion occurs because individuals are motivated to identify with sources they find appealing or similar to themselves, leading to attitude change that is often more affective and potentially less stable over time.

Subsequent research has increasingly treated source credibility and source attractiveness as complementary rather than competing perspectives. While credibility-based influence is driven by cognitive evaluations of message validity, attractiveness-based influence relies on affective and social identification processes. Importantly, these dimensions are conceptually independent: a source may be perceived as expert without being attractive, or attractive without being expert, and each dimension contributes differently to persuasion outcomes (Seiler & Kucza, 2017).

In marketing and advertising, Source Credibility Theory has been extensively applied to understand endorsement effectiveness. Expert endorsers are particularly effective for high-risk or technologically complex products, as their perceived expertise and trustworthiness reduce uncertainty and perceived risk (Biswas et al., 2013). By contrast, celebrity or attractive endorsers often operate through identification mechanisms, making them more suitable for low-involvement or image-driven products. Research on humor in advertising further illustrates the relevance of source credibility: humorous messages are more persuasive when attributed to credible sources, as credibility reduces the risk that humor distracts from message comprehension and acceptance (Sternthal & Craig, 1973). Overall, Source Credibility Theory provides a robust and enduring framework for understanding how source characteristics shape consumer responses to persuasive communications.

References

Biswas, D., Biswas, A., & Das, N. (2013). The differential effects of celebrity and expert endorsements on consumer risk perceptions: The role of consumer knowledge, perceived congruency, and product technology orientation. Journal of Advertising, 35(2), 17–31.

Hovland, C. I., Janis, I. L., & Kelley, H. H. (1953). Communication and persuasion. Yale University Press.

McGuire, W. J. (1985). Attitudes and attitude change. In G. Lindzey & E. Aronson (Eds.), Handbook of social psychology (Vol. 2, pp. 233–346). Random House.

Seiler, R., & Kucza, G. (2017). Source credibility model, source attractiveness model and matchup-hypothesis: An integrated model. Economy & Business, 11, 1–11.

Sternthal, B., & Craig, C. S. (1973). Humor in advertising. Journal of Marketing, 37(4), 12–18.